Well jar



R. C. MONROE WELL JAR Filed Feb. 24, 1967 sept. 3, 1968 By ML ATTORNEYUnited States Patent 3,399,741 WELL `lAR Robert C. Monroe, Houston,Tex., assgnor to Schlumberger Technology Corporation, Houston, Tex., acorporation of Texas Filed Feb. 24, 1967, Ser. No. 618,403 5 Claims.(Cl. 175-297) ABSTRACT OF THE DISCLOSURE A hydraulic mechanism in aIwell jar provides a time delay by means of a piston moving in acompression bore to compress a hydraulic iluid in a chamber. The pistonis release-d upon its movement into an enlarged bore to produce a largejar-ring in the mechanism. A normally open bypass valve is provided inthe system to increase the bypass of fluids around the piston, whichlimits the amount of uid pressure generated in the chamber and therebylimits the amount of the jarring force. However, the bypass valve isarranged to close upon the application of a large force to the movingpiston which, in turn, permits an increased pressure and a much largerjarring force to be generated by the mechanism. Therefore, the systemprovides a means for selectively permitting a light or heavy jarringforce to be applied to a stuck object in a well bore.

Background of the invention This invention relates to a well jar, and,more particularly, to a hydraulic well jar having means for selectivelypermitting -a light or heavy jarring -force to be applied to an objectstuck in a well bore.

In the oil industry, jars are used on a wireline or string drill pipefor the purpose of providing, when needed, an impact force to a partstuck in a well bore. Jars operate on the principle of a hammer memberstriking an anvil member to deliver a large impact for-ce to the stuckpart. A hydraulic jar uses a hydraulically timed delay for the purposeof developing large lforces within a hydraulic system 'in the wellwhich, when released, impact the hammer on the anvil generating a largeshock force on the stuck part. The time delay in such a System typicallyis provided by restricting flow of hydraulic fluids between `telescopingmembers while the hammer member moves toward the anvil member. Thisrestricted flow is `dependent upon the size of a restricted orificeformed between telescoping jar members. As will be appreciated, suchrestriction of hydraulic fluids between the telescoping memberscompresses the hydraulic fluid to produce tremendous forces within thejar. Thus, the rate of such restricted uid ow is determinative of theamount of force to be developed by the jar mechanism. l

In certain applications, it is desirable to impart a light jarring forceto a stuck object. A jar used in a coring operation is typical of such asituation. In a coring operation, the jarring force is used to break offa core being taken by a coring mechanism in -a well bore. In such anapplication, too large a jarring force willfoften damage the core. Onthe other hand, where the jar is used to remove a stuck piece ofequipment from the well bore, a much larger jarring force is desirable.

It is, therefore, Idesirable to have a single jar mechanism which may beused in either =a light or heavy jarring situation. The all purpose jaralleviates the need of building and maintaining special purpose jars andthe all purpose jar permits the application of light and heavy jarringforces at all times in any type operation. For instance, if during acoring operation, a portion of the tool string becomes stuck, a largejarring force may be applied to remove the stuck portion, while at thesame time the jar. However, this method takes an undesirably long timeperiod to operate the delay mechanism. In order to overcome this timedisadvantage, a light oil is sometimes used in the jar mechanism topermit faster metering of oil through the hydraulic delay thuspermitting the jar to operate faster under low pull conditions. If,however, the coring device `or other portion of the tool should becomestuck in the well bore, the light oil precludes a suticient delay timeto permit a heavy jarring force to be applied to the stuck object.

Accordingly, it is yan object of the present invention to provide a newand improved well jar which selectively permits a light Ior heavyjarring force to be applied to an object stuck in a well bore.

Summary ofthe invention Apparatus in accordance with the presentinvention includes a hydraulic well jar having an anvil, a hammer, andhydraulic delay mechanism. In the hydraulic delay mechanism, `whentension is -applied to the jar, a valve piston tted relative to acompression bore provides a restricted annular space which regulates theby-pass of uid while the piston compresses fluid in a chamber. Anenlarged bore is 'formed at the upper end of the cornpression bore. Aselectively operable secondary bypass means provides for acceleratedfluid tlow around the valve piston during its movement in thecompression bore. This secondary bypass means includes a spring-loadedvalve which is normally open to provide for such an `accelerated iluidbypass. However, upon the application of a large tension force to thepiston, the resulting pressure Igenerated in the chamber closes thesecondary bypass valve so that all uid flowing past the piston must owthrough the restricted annular space. The secondary valve is adjustableto permit regulation of the pressure required to close the secondarybypass. As soon as the piston exits from the compression bore into theenlarged bore, iuid freely bypasses the piston .and the hammer isaccelerated and comes into contact with the anvil to provide the jarringimpact force. To reset the jar, the hammer is moved back to its originalposition where the valve piston is in the compression bore.

The novel features of the present invention are set forth withparticularity in the appended claims. The present invention, both as toits organization and manner of operation together with further objectsand advantages thereof, may best be understood by way of illustrationand example of certain embodiments when taken in conjunction with theaccompanying drawings.

Brie)c description of the drawings FIGURE 1 is a cross-sectional view ofa well jar embodying concepts of the present invention;

FIGURE 2 is an enlarged view of the hydraulic section of the apparatusshown in FIGURE 1; and

FIGURE 3 is 'an enlarged view of the secondary bypass valve shown inFIGURE 2.

Description of the preferred embodiment Referring irst to FIGURE 1, thehydraulic well jar 10 includes a telescopically mounted mandrel 11 andhousing 12. The mandrel 11 at its upper end has external splines 13received within internal splines 14 on the housing permitting rotationof the drill string through the jar and at the same time also permittinglongitudinal, nonrotative movement between the housing and mandrel.

The mandrel 11 has upper and lower sections 15, 16 of identicaldiameter, the upper section 15 being received within an upper borev 17in the housing while the lower section is received within the bore 18 ofan annular piston 19 slidably mounted within a bore 20 in the housing.High pressure sealing means are provided between the mandrel and housingat 12a and on the piston 19. The equal diameter sections 15, 16 of themandrel provide for pressure balancing of the mandrel while the piston19 compensates for volume changes in a fluid received in a hydraulicchamber 29 between the mandrel and the housing. The mandrel 11 below thefloating piston 19 is sized to a diameter somewhat less than the bore 21of the housing to permit well bore uid access to the oating piston 19.

The housing 12 has an enlarged bore 22 which forms a downwardly facingshoulder 23, the shoulder being the jar anvil. The mandrel 11 isprovided with an annular enlargement having an upwardly facing shoulder23a forming a hammer.

The hydraulic system of the jar is shown in greater letail in FIGURE 2and further includes valved piston means provided on the mandrel belowthe hammer 23a in the form of an enlarged flange 24 on the -mandrel onwhich a tubular metal sleeve 25 sets. The abutment of the lower end ofthe sleeve with the upper side of the flange forms a metal-to-rnetalfluid seal. The sleeve is normally urged toward the enlarged ange by anannular ring 26 slidably received on the mandrel 11 `and a compressionspring 27 positioned between the ring 26 and lower portion of themandrel hammer 23a. The annular ring 26 has a lower base portionslidably mounted on the mandrel, the base portion having longitudinalbypass ports 2S. The tubular sleeve 25 is slidably received within acompression bore in the housing which adjoins the lower end of theenlarged bore 22 of the fluid chamber 29. Sleeve is slidably mounted onan enlarged splined portion 32 of the mandrel. The fit between thetubular sleeve and compression bore is such that a restricted annularspace is provided to meter uid past the sleeve 25. A threaded mechanismis provided at the upper end of the mandrel 11 and acts between themandrel and housing. The mechanism 30 permits selective adjustment ofthe distance to which the sleeve 25 extends into the compression bore 20thereby providing a selective adjustment of the time delay for operatingthe jar. The jar mechanism thus far described is set forth in greaterdetail in U.S. Patent No. 3,251,426.

Operation of the apparatus described thus far is briey as follows: Thejar is coupled in a drill string for use in the usual Idrilling, testingor other such operations in a well bore. It the drill string becomesstuck, the operator determines the tension to be applied, pulls tensionon the drill string and locks the drill string at the desired tension inthe drill stand. In the jar, the housing 12 is attached to the stuckportion while the mandrel 11 has tension applied thereto. The mandrelfirst moves slowly upward relative to the housing because the valvepiston means, including the sleeve 25, compresses the fluid contained inthe fluid chamber 29. The rate of movement is controlled by the rate atwhich the compressed fluid bypasses the piston between the sleeve 25 andcompression bore 20. Slow movement of the piston means continues untilthe tubular sleeve 25 exits from the compression bore 20 into theenlarged bore 22 whereupon the jar is tripped because Huid :may nowrapidly bypass between the housing 12 and sleeve 25. This, in turn,permits a rapid relative movement between the mandrel and the housingwhich terminates with an impact of the hammer 23a upon the anvil 23. Ifthe pipe, tool, or other object is still stuck, the operator repeats theoperation. To reset the jar, the mandrel is moved downwardly and thetubular sleeve 25 will move upwardly so that uid may bypass between thesleeve 25 and mandrel and permit a quick resetting of the valve pistonmeans to its initial position in the compression bore. By means of thethreaded mechanism 30, the amount of time required for the 4 i4 l pistonmeans to move through the compression bore 20 and exit into the enlargedbore 22 can be selectively adjusted.

As set forth in the background of the invention, some jarringapplications, for example jars used in coring operations, require arelatively light force to be applied to the stuck object, i.e., thecore. If the jar, however, is designed for the application of heavyloads to remove a stuck tool in the well, it is readily seen that theuse of the jar for both purposes would lead to drawbacks in theoperation of the tool in one or the other or both types of applicationsfor which a jar is used. For example, if the jar is constructed to beoperated with a heavy force applied to the stuck object, the pistonmeans is designed to operate in `a certain amount of time to generatethe forces required and release them thus setting up the jarring blow.lf, however, it is desired to pull a light load on the same jarring toolin order to produce a light jarring force, it would take an extremelylong period of time to operate the piston means for tripping the ar. JBy means of the present invention, the jar may be selectively operatedto produce large jarring forces for removing stuck tools or lightjarring forces to break off cores for example. To accomplish this, asecondary bypass valve 33 is provided in the hydraulic system. Thesecondary bypass valve communicates the hydraulic systern above andbelow the enlarged ange 24 on the mandrel.

The valve device 33 is shown in greater detail in FIG- URE 3 andincludes a vertical passageway 34 which connects the upper side of theenlarged flange 24 with an enlarged vertical bore 36 communicating withthe lower side of the enlarged flange 24. A valve housing 38 isthreadedly received within the bore 36 and has seal means 39 at itsupper tapered end to provide a fluid-tight seal between the valvehousing and the bore 36. An annular valve seat 41 is threadedly receivedwithin a bore 35 in the valve housing 38. Seal means are positionedbetween the housing 38 and the valve seat 41. A passageway 40 in theupper end of the valve housing connects the bore 35 with the passageway34. The upper end of the valve seat 41 has a frusto-conical surface 42.A valve member 43 is movably received within bore 35 between the upperend of the valve housing 38 and the valve seat 41. A frusto-conicalsurface 46 is formed on the lower side of the valve member 43 which,when engaged with the surface 42 on the valve seat, provides afluid-tight seal which prevents communication of fluid through thesecondary valve 33. An upper axial bore 47 is formed in the valve member43. Ports 48 are provided in the valve member to provide fluidcommunication between the axial bore 47 and the exterior of the valvemember. The valve member 43 is sized to provide a space 49 between thevalve member and the interior bore 35 of the valve housing. The valveseat 41 has a longitudinal axial bore 52 extending therethrough. Aspring retainer nut 53 is threadedly received in the lower end of bore52. A spring 54 is positioned between the retainer nut 53 and the lowerside of the valve member 43.

The operation of the secondary bypass valve 33 is as follows. If it isdesired to produce a small jarring force as in the case of a coringoperation, an upward pull is applied to the drill string and thus themandrel on the jar, the housing being attached to the coring device,etc. If a light pull is applied to the string of pipe, fluid will meterbetween the tubular sleeve 25 and compression bore 20 in the normalfashion. In addition, lluid will also bypass through the secondary valvesystem 33, the spring 54 in the secondary valve system beingsufliciently strong to maintain the valve member 43 spaced from thevalve seat 41. This permits fluid to pass downwardly from the highpressure, upper side of the flange 24 through the passageways 34, 40into bore 47 of the valve member 43, through the ports 48, into theannular space 49, downwardly into the bore 52 of the valve seat andthrough the bore of the spring retainer nut 53 which communicates withthe lower or low pressure side of the flange 24. This passage of fluidthrough the secondary bypass valve permits the application of lightforces to the jar mandrel to trip the jar in a reasonably short periodof time. As the upward force is continually applied to the mandrel, thesleeve 25 and enlarged flange 24 move upwardly into the chamber 29whereupon the mandrel accelerates upwardly to bring the hammer 23a intocontact with the anvil 23 to produce the jarring force.

If, on the other hand, it is desired to apply a large jarring force toan object which is stuck in the well bore, for example, if the coringdevice should become stuck in the well bore, such large force is appliedas follows. A heavy pull is taken on the pipe string and thus applied tothe mandrel of the jar. Such heavy pull generates a large llow of oil tocreate a pressure increase in the passageway 40 which is suicient toovercome the force of spring 54. Thus, the valve member 43 is moveddownwardly against the force of the spring 54 to mate the surface 46 onthe valve member with the surface 42 on the valve seat thereby providinga metal-to-metal seal and preventing passage of iluid through the bore52 in the valve seat. It is readily seen that the greater the pull onthe mandrel, the greater the ow through passageway 40, with theresulting higher pressure acting on the valve members to create atighter seal. With the secondary passage closed, uid can only bypassbetween the sleeve 25 and compression bore 20 thus permitting a heavyload to be applied to the jar mechanism due to the increasedrestriction, which in turn generates a large jarring force.

The spring retainer plug 53 is threadedly received within the bore 52 ofthe valve seat to permit a selective pretensioning of the spring 54 sothat the secondary bypass 33 may be adjusted to operate at any desiredpressure differential, thereby determining the amount of force which isnecessary to close the secondary bypass which in turn changes theoperation of the jar from a low force to a high force jar.

While a particular embodiment of the present invention has been shownand described, it is apparent that changes and modilications may be madewithout departing from this invention in its broader aspects and,therefore, the aim in the appended claims is to cover all such changesand modifications as fall within the true spirit and scope of thisinvention.

What is claim is:

1. A hydraulic well jar including telescopically mounted mandrel andhousing members movable between contracted and extended positions, saidmembers having anvil and hammer means thereon, said anvil means beingspaced from said hammer means when said members are in said contractedposition and arranged for contact when said members are in said extendedposition, a sealed hydraulic chamber between said members and adapted toreceive a hydraulic fluid, hydraulic means in said chamber coupled toone of said members and movable relative to the other of said members,said hydraulic means cooperating with said members during movement overa rst relative distance from said contracted position toward saidextended position to compress fluid in said chamber and permit a limitedbypass of fluid and cooperating with said members when moved beyond:said first distance to permit a relatively free bypass of fluid, andselectively operable valve means in said hydraulic means for bypassinguid in addition to said limited bypass of fluid as said hydraulic meansis moved through said first relative distance.

2. A well jar apparatus comprising: telescopically arranged mandrel andhousing members adapted for limited relative movement between contractedand extended positions; and hydraulically operable means includingpiston means on one of said members and first bypass means for-bypassing tluid between said piston means and the other of said membersto retard relative movement of said members during a portion of saidrelative movement between said positions, said hydraulically operablemeans further including second bypass means which can be selectivelyoperated in order to bypass uid past said piston means in order to varythe retarding effect of said hydraulically operable means.

3. The apparatus of claim 2 wherein said second bypass means includesvalve means responsive to fluid pressure generated on one side of saidpiston means for c011- trolling llow rate past said piston means.

4. The apparatus of claim 3 further including means for adjusting saidvalve means to operate at preselected pressures.

5. A well jar `apparatus. comprising: inner and outer members arrangedfor longitudinal relative movement between contracted and extendedpositions, said members having means engageable in one of said positionsto provide a jarring 'blow to an object connected to one of saidmembers; and hydraulic means for retarding relative movement `of saidmembers toward said one position only during a portion of said relativemovement, said hydraulic means including irst and second normally openbypass means, one of which is closable in response to a preselectedforce applied to the other of said members.

References Cited UNITED STATES PATENTS 2,678,805 5/ 1954 Sutlif 175-2973,087,559 4/1963 Hazen et al. 175-297 3,251,426 5/1966 Lebourg 175-2973,349,858 10/ 1967 Chenowe'th 175-297 DAVID H. BROWN, Primary Examiner.

